The broadband brightfield/darkfield wafer inspection system provided
receives broadband brightfield illumination information via a defect
detector, which signals for initiation of darkfield illumination. The
defect detector forms a two dimensional histogram of the defect data and
a dual mode defect decision algorithm and post processor assess defects.
Darkfield radiation is provided by two adjustable height laser beams.
Vertical angular adjustability is provided by modifying cylindrical lens
position to compensate for angular mirror change by translating an
adjustable mirror, positioning the illumination spot into the sensor
field of view, rotating and subsequently moving the cylindrical lens.
Light level control for the system is provided by a dual polarizer first
stage. Light exiting from the second polarizer passes through a filter
which absorbs a portion of the light and comprises the second stage of
light control.